Improving tropical rainfall simulation in our national climate model

31 July 2018

Climate models allow us to recreate past climates and simulate possible climates of the future. Rainfall is one of the most important weather elements that affects our day-to-day lives, so accurate simulations of rainfall in Australia’s national climate model, ACCESS, are an important part of climate change science information, data and services. Better simulations of rainfall across Australia will enable better forecasting on daily through to seasonal timescales, and allow for multi-year to multi-decadal projections.

Realistically simulating rainfall, especially tropical rainfall, remains a significant challenge for researchers in Australia and across the globe when developing climate and atmospheric models. Improving ACCESS to better simulate tropical rainfall is an active area of research for the Earth Systems and Climate Change Hub.

Rainfall in the tropics is largely controlled by atmospheric convection (the vertical movement of warm and cool air in the atmosphere), so understanding the physical processes that are involved is important for ensuring it is accurately represented in models. To do this, Hub researchers have improved the existing tropical convection scheme (representation) within ACCESS and have developed a concept for a new scheme to represent tropical convention even more accurately in ACCESS in the future.

Thanks to the work of Hub researcher Dr Hongyan Zhu and her collaborators, ACCESS now better represents tropical rainfall and the Madden-Julian Oscillation (an important driver of tropical variability over the one-to-two month time scale). These model improvements have been recognised by the international climate science community, including the UK Met Office. The Met Office has included these improvements into their equivalent climate and atmospheric model (the UK Met Office Unified Model), on which ACCESS is based.

Hub researchers have also developed a new convection scheme that improves the simulation of tropical rainfall and its variability within seasons. A version of this new convection scheme has been implemented in ACCESS and its impact on simulated rainfall is now being examined. In the future, Hub researchers plan to implement and test a more comprehensive version of this scheme in ACCESS to further enhance rainfall simulations.

Through this research and development of our national climate model, our researchers now have an improved understanding of how convection schemes within ACCESS work to improve the skill of our climate models in simulating tropical rainfall. This will lead to better simulations and projections of tropical rainfall and allow analysis of the potential impacts a warming climate will have on tropical rainfall patterns in Australia into the future.

Read more about how research undertaken by the Hub is improving the physical processes which underpin ACCESS.

Interested in how rainfall may change in Northern Australia? Read more here.